Buttered Popcorn Flavor???

Holy buttered popcorn batman!! I have brewed 3 all-grain recipes in the last 3 months, and ALL of them have this "off flavor" of buttered popcorn.

Now, the lager I tried to make, I froze by accident becuase I did not program my "programmable thermostat" correctly. I thawed it out, pitched new yeast..fermented again in the cooler, brought it up in temp for a week then crashed it, but THAT did not work!

I tried to make an all-grain Oktoberfest and a Imperial Blond Ale. Both brews ended up with that butter flavor.

I was reading about how the diacetyls will give that flavor, but I can not see how to regulate the level of diacetyls based on the brewing instructions.

I have NO issues with diacetyls when I extract brew, only when I do an all grain recipe.

PLEASE, someone help me figure this out.

Many thanks.

Try another yeast strain. Oxygenate wort before fermentation. Reduce primary fermentation temperature. Use a
warmer/longer secondary fermentation. Use healthy yeast in sufficient quantity. Make sure sufficient yeast nutrients
are available (including reducing adjunct use). Check for infection. Allow beer to rest on yeast until fully attenuated.
Don’t rack, filter or fine too early. Don’t crash-cool yeast. If lager, raise temperature for a diacetyl rest at end of
fermentation. Bottle condition beer at cellar temperatures. Avoid adding oxygen during fermentation.

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http://www.bjcp.org/docs/Beer_faults.pdf

Diacetyl in a lager is usually caused by stressed yeast. Are you pitching the correct number of cells for your beer? This is about 1.5m cells per mL per degree plato of your wort for lagers, and about 750,000 cells/m/P for ales. Use a calculator like YeastCalc or MrMalty to figure out how large of a starter to make. If you're having diacetyl problems in your lagers, after the initial fermenation is 80% finished, warm up your lager for a diacetyl rest to 62F or a bit warmer so the yeast can reabsorb the diacetyl.

Low oxygenation can also cause diacetyl in lagers, and also in ales. You should be oxygenating to ~10ppm dO2 with pure O2 to do lagers. British ale yeasts, in particular, are more known for throwing diacetyl than other ale strains, they all LOVE oxygen and will get buttery without it.

The final culprit could be infection, although this is the least likely problem. Both lacto and pedio can throw diacetyl, but you'll usually get some other distinctive off-flavors (sour and funky).

My guess is you are under-pitching or under-oxygenating, since from your description you are performing a "diacetyl rest" of sorts which under normal circumstances would help clean that up.

If you aren't making a sizable starter for your lagers, you are definitely not pitching enough yeast. You should also be aerating your wort quite a lot, or ideally, bubbling pure oxygen with an aeration stone into the wort prior to pitching.

Can you post some more information on your fermentation process, times, temperatures, yeast, pitch rate, oxygenation method etc? I has a similar experience with a Beirmunchers Cream of 3 crops cream ale right after I got my fermentation chamber, the issue was I never performed a proper Diacetyl rest at the end of the ferment. It tasted like pure buttered popcorn, disgusting and I ended pitching the whole batch, after trying several different ways to save it. Now I always raise the temp to around 72 degrees for 3 days at the end of fermentation and never had an issue since,